1. Field of the Invention
The present invention relates to a magnetic recording medium capable of writing and reading digital data, as well as a magnetic recording/reproducing apparatus for the same.
2. Description of the Related Art
In a magnetic recording medium, for example in a floppy disk or a hard disk, digital information is written in a predetermined format using a head, then is read as necessary, and a corresponding processing is executed using a personal computer or the like. These types of magnetic recording mediums are constituted by applying a magnetic material onto the surface of a thin, disk-like, resinous sheet.
Standards have been established for this type of magnetic recording mediums. According to the standards, head tracing paths, called tracks, are prescribed concentrically from the outside toward the center, each track is divided in the circumferential direction, and each divided recording unit is designated a sector. For each sector is prescribed a format comprising an ID field, a gap, a data field and a gap successively in order of writing and reading. Data which has been written in a certain format cannot be read out unless the same format is followed.
In the case of such magnetic recording mediums as a floppy disk and a hard disk, unlike CD-ROM or the like, it is possible to select writing (W) and reading (R) arbitrarily.
In the above prior art, there is no distinction between reading (R) and writing (W), and the magnetic recording medium is employable for both reading and writing. Therefore, track density is set to the same density throughout the whole region thereof. Further, the time width of servo information in a data format is set to the same width for both reading and writing.
Consequently, in the case of reading only, it is not required to take a wide track margin between tracks, which however is set to the same degree as in writing (at the time of writing it is necessary to take the track pitch somewhat large in consideration of both variations in magnetic head characteristics between apparatuses and the follow-up characteristics of a tracking servo mechanism so as to prevent destruction of data caused by interference with data of the adjacent track). This has been an obstacle to the improvement of the memory capacity (track density).
Further, in recording servo information in the data format region, AGC (automatic gain control) is once reset and thereafter the writing of servo information is performed. Therefore, taking the time required for AGC circuit to rise into consideration, it is necessary to set the time width of a servo preamble portion of the servo information, to be relatively long thus resulting in that it is required to make the time width of the servo information long. Also from this point, a difficulty has been encountered in increasing the memory capacity.